CVE-2026-59859: Microsoft Kiota Code Generation Literal Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jqwh-526h-c92j",
  "modified" : "2026-08-17T14:53:45Z",
  "published" : "2026-07-24T15:46:46Z",
  "aliases" : [ "CVE-2026-59859" ],
  "summary" : "Microsoft Kiota: Code Generation Literal Injection in Kiota PHP Generator",
  "details" : "# Impact\n\nThe Kiota PHP code generator is vulnerable to a code generation literal injection attack. The generator embeds string values from OpenAPI fields (e.g. `description`, default values, and property names) directly into PHP double-quoted string literals without properly escaping the `$` character. Since PHP evaluates string interpolation expressions like `\"${expr}\"`, `\"$var\"`, and `\"{$obj->prop}\"` within double-quoted strings at runtime, an attacker who controls an OpenAPI specification file can inject arbitrary PHP code into generated model and request-builder classes.\n\n# Who is impacted\n\nDevelopers using Kiota to generate PHP API clients from external or untrusted OpenAPI specifications\n\nTeams with CI/CD pipelines configured to automatically regenerate client code from remote specs\n\nApplications that deploy generated PHP code to production servers\n\n# Vulnerability details\n\nAffected component: `StringExtensions.cs`\n\nRoot cause: The shared `SanitizeDoubleQuote()` function in `Writers/StringExtensions.cs` does not escape the `$` character. As a result, any schema-derived string emitted as a PHP double-quoted literal preserves `$`-prefixed interpolation constructs (`${...}`, `$var`, `{$...}`) verbatim, which PHP evaluates at runtime instead of treating as literal text. This is the same class of code-generation literal-injection flaw previously fixed for the Ruby generator (`#` interpolation), recurring here as a missed variant for PHP's `$` interpolation in the sibling sanitizer helper.\n\n# Attack vectors\n\nOpenAPI `description` and default fields in schema properties\n\nProperty wire-name keys embedded in deserializer/serializer methods\n\nAny schema-derived string embedded in PHP double-quoted literals\n\nSeverity: Critical when generated code reaches production; High for CI/CD environments with access to production secrets; Medium for public third-party specs; Low for developer-controlled specs.\n\n# Patches\n\n[#7863](https://github.com/microsoft/kiota/pull/7863)\n\n# Workarounds\n\nIf you cannot upgrade immediately:\n\n1. Audit and sanitize OpenAPI specifications: Review all OpenAPI specification files for any descriptions, default values, or property names containing the `$` character. Remove or replace any suspicious strings before code generation.\n2. Code review of generated files: Implement mandatory code review of all generated PHP files before merging into any branch. Look for double-quoted strings containing `${`, `$var`, or `{$` patterns.\n3. Restrict specification sources: Only consume OpenAPI specifications from trusted internal sources. Avoid automatic code generation from external or third-party APIs until this patch is applied.\n4. Isolate generated code from production: Do not deploy generated PHP models to production environments unless the specification source has been verified and reviewed.\n5. Manual escaping (temporary): If regeneration is not possible, manually inspect and edit generated files to escape any `$` characters in double-quoted string literals (replace `$` with `\\$`).\n\n# Remediation\n\nUpgrade Kiota to 1.29.1, 1.32.4, or later.\n\nRegenerate/refresh existing generated clients as a precaution:\n\nRefreshing generated clients ensures previously generated vulnerable code is replaced with hardened output.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.30.0"
      }, {
        "fixed" : "1.32.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota.Builder"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.30.0"
      }, {
        "fixed" : "1.32.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.29.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota.Builder"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.29.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/security/advisories/GHSA-jqwh-526h-c92j"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-59859"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/pull/7863"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/commit/5e2a211ac4261988fbdc72c3b268596ea8837b87"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/microsoft/kiota"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/releases/tag/v1.32.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T15:46:46Z",
    "nvd_published_at" : "2026-07-16T15:16:35Z"
  }
}